In general, a printed circuit board (PCB) is manufactured by using a copper clad laminate in which a conductive layer is laminated on an insulating member. The PCB can be manufactured by forming circuit patterns on the copper clad laminate, which is called an electric PCB. Since the electric PCB uses conductive metals, such as copper, as electric interconnections for transmitting signals, the electric PCB represents limitations in transmission of mass storage date.
In order to solve the above problem, recently, an optical PCB including an optical wave guide formed on an insulating member has been developed. In order to form the optical wave guide serving as an optical path in the optical PCB, optical fiber including polymer or glass fiber is employed.
FIG. 1 shows a sectional view of an optical PCB according to the related art as well as a partially enlarged view of the optical PCB.
Referring to FIG. 1, an optical wave guide 101 is laminated on the optical PCB 104. The optical wave guide 101 includes an optical path changing part 102, which is bent at the right angle to change an optical path at the right angle.
In the case of the optical PCB 104 formed with the optical wave guide 101 accommodated therein, the final thickness of the optical PCB 104 may depend on the thickness t of the optical wave guide 101.
As shown in the partially enlarged view of FIG. 1, the thickness t of the optical wave guide 101 refers to the distance from a horizontal section of the optical wave guide 101 to a tip of a bending section of the optical wave guide 101. If the optical wave guide 101 is vertically laminated, a section 103 of the optical wave guide 101 exposed through a top surface of the optical PCB 104 has an area equal to a vertical sectional area of the optical wave guide 101. If the optical wave guide 101 has a small sectional area, light alignment is difficult.
If the thickness of the optical wave guide 101 is reduced in order to reduce the thickness of the optical PCB 104, the optical wave guide 101 must be bent with a smaller radius of curvature, so the optical wave guide 101 may be easily broken.
As described above, if the optical wave guide is vertically laminated, the section of the optical wave guide exposed through the top surface of the optical PCB has the area equal to the vertical sectional area of the optical wave guide, and the light alignment is difficult if the optical wave guide has a small sectional area.
In addition, since the optical path changing part is manufactured by bending the optical wave guide at the right angle to change the optical path at the right angle, light loss may be generated due to the bending structure of the optical wave guide and the optical wave guide may be broken caused by high tension as the bending work is carried out. For this reason, the thickness of the optical PCB is inevitably increased.